This invention relates to improving a type of virtual computer system that runs guest OSs on a plurality of physical computers.
The recent computers consume more electric power as the performance of processors (CPUs) becomes higher. In particular, CPUs for server use which are equipped with a large-capacity cache memory have high performance but consume a great deal of power. Power consumption in a server where a plurality of CPUs are installed is even greater. In data centers and other facilities that run a large number of servers, large power consumption in the servers has an accordingly large influence on server installation conditions, cooling, and the like.
IT systems using a server are generally designed according to the peak CPU performance. Consequently, the number of servers with a low CPU operation ratio is large in data centers and other facilities that run a large number of servers. While the recent CPUs employ a technique of reducing power consumption by changing the operating clock or changing the drive voltage of the CPU, a light-load state (e.g., idling state or standby state) does not equal zero power consumption. This is why server virtualization (virtual machine) technology which improves the CPU operation ratio by integrating a plurality of servers into one server is attracting attention.
Known examples of the server virtualization technology include VMware® ESX Server which runs a plurality of guest OSs on a host OS as disclosed in an Internet article titled “VMware ESX Server”, published by VMware, Inc., and retrieved at URL: http://www.vmware.com/files/jp/pdf/esx_datasheet.pdf, on Nov. 1, 2007 (hereinafter referred to as Non-patent Document 1), and in JP 2006-113767 A. A known example of the virtualization technology that uses a hypervisor is Xen by XenSource, Inc. (now Citric Systems, Inc.) as disclosed in an Internet article titled “Xen 3.0 Datasheet”, published by XenSource, Inc., and retrieved at URL: http://www.vmware.com/files/jp/pdf/esx_datasheet.pdf, on Nov. 1, 2007 (hereinafter referred to as Non-patent Document 2).